System studies of the use of industrial excess heat

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LINKÖPING STUDIES IN SCIENCE AND TECHNOLOGY.

DISSERTATION NO. 1679

System studies of the use of industrial excess heat

SARAH BROBERG VIKLUND

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System studies of the use of industrial excess heat SARAH BROBERG VIKLUND

ISBN978-91-7519-042-6

Linköping Studies in Science and Technology, Dissertation No. 1679 ISBN978-91-7519-042-6

ISSN 0345-7524

Distributed by:

LINKÖPING UNIVERSITY

Department of Management and Engineering SE-581 83 Linköping

Sweden

Phone: +46 (0)13-28 10 00

Printed by:

LiU-Tryck, Linköping, Sweden, 2015 Cover design by Per Lagman, LiU Tryck

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This thesis is based on work conducted within the interdisciplinary graduate school Energy Systems. The national Energy Systems Programme aims at creating competence in solving complex energy problems by combining technical and social sciences. The research programme analyses processes for the conversion, transmission and utilisation of energy, combined together in order to fulfil specific needs.

The research groups that constitute the Energy Systems Programme are the Department of Engineering Sciences at Uppsala University, the Division of Energy Systems at Linköping Institute of Technology, the Research Theme Technology and Social Change at Linköping University, the Division of Heat and Power

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Division of Energy Systems

Department of Management and Engineering Linköping University

ABSTRACT

Energy, materials, and by-products, can be exchanged between companies, having positive effects in the form of improved resource efficiency, environmental benefits, and economic gains. One such energy stream that can be exchanged is excess heat, that is, heat generated as a by-product during, for example, industrial production. Excess heat will continue to play an important role in efforts to reduce greenhouse gas (GHG) emissions and improve energy efficiency. Using excess heat is therefore currently emphasized in EU policy as a way to reach EU climate targets.

This thesis examines the opportunities of manufacturing industries to use industrial excess heat, and how doing so can positively affect industry, society, and the climate. Since different parts of the energy system are entangled, there is an inherent complexity in studying these systems and introducing excess heat in one part of the energy system may influence other parts of the system. This analysis has accordingly been conducted by combining studies from various perspectives, by applying both quantitative and qualitative methods and covering a broad range of aspects, such as technical possibilities as well as climate, policy, economics, and resource aspects.

The results identify several opportunities and benefits accruing from excess heat use.

Although excess heat is currently partly used as a thermal resource in district heating in Sweden, this thesis demonstrates that significant untapped excess heat is still available. The mapping conducted in the appended studies identifies excess heat in different energy carriers, mainly low-temperature water. Analysis of excess heat use in different recovery options demonstrated greater output when using excess heat in district heating than electricity production. Optimizing the trade-offs in excess heat used in a district heating network, heat- driven cooling, and electricity production under different energy market conditions while

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other hand, depend on the energy market development, for example, the marginal electricity production and marginal use of biomass, and on the type of district heating system replaced.

The interviews performed reveal that energy policy does influence excess heat use, being demonstrated both to promote and discourage excess heat use. Beyond national energy policies, internal goals and core values were identified as important for improved energy efficiency and increased excess heat use.

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Avdelningen Energisystem

Institutionen för ekonomisk och industriell utveckling Linköpings Universitet

SAMMANFATTNING

Energi, material och biprodukter kan utbytas mellan företag och därmed leda till positiva effekter i form av förbättrad resurseffektivitet, miljövinster och ekonomiska vinster. Ett sådant energiflöde som kan nyttjas är industriell överskottsvärme, det vill säga, värme som genereras som en biprodukt vid till exempel industriell produktion. Överskottsvärme kommer att fortsätta att spela en viktig roll i arbetet med att minska utsläppen av växthusgaser och öka energieffektiviteten och lyfts därför fram i EU policy som ett sätt att nå klimatmålen.

Denna avhandling undersöker möjligheterna för den tillverkande industrin att använda industriell överskottsvärme och hur detta kan medföra positiva bidrag till industrin, samhället och klimatet. Eftersom olika delar av energisystemet påverkar varandra så finns en inneboende komplexitet i att studera dessa system. Användningen av överskottsvärme i en del av energisystemet kan alltså påverka andra delar av systemet. Denna analys har därför gjorts genom att kombinera studier från olika perspektiv, genom användning av både kvantitativa och kvalitativa metoder och genom att täcka in ett brett spektrum av aspekter såsom tekniska möjligheter, och klimat-, policy-, ekonomiska- och resursaspekter.

Resultaten visar flera möjligheter med, och fördelar som kommer från, användning av överskottsvärme. Även om överskottsvärme redan idag delvis används som värmekälla i fjärrvärme så visar denna avhandling att tillgången på outnyttjad överskottsvärme fortfarande är betydande. Kartläggningen som genomfördes identifierar överskottsvärme i olika energibärare, i huvudsak i vatten med låg temperatur. Användningen av överskottsvärme analyserades för olika användningsalternativ och visade på en större output vid användning i fjärrvärmesystemet än när den användes för elproduktion. När fördelningen av användning av överskottsvärme mellan utnyttjande i fjärrvärmesystemet, för produktion av kyla eller el

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elanvändningen minskar utsläppen av växthusgaser. Effekterna från överskottsvärme i fjärrvärme beror däremot på energimarknadens utveckling, såsom framtida elproduktion och alternativanvändning av biomassa, och på vilken typ av fjärrvärmeproduktion som ersätts.

Intervjuerna som utförts visar att styrmedel påverkar överskottsvärmeanvändningen.

Styrmedel visade sig både främja och missgynna användningen av överskottsvärme. Utöver nationella styrmedel så lyftes även interna företagsmål och kärnvärden fram som viktiga för ökad energieffektivitet och ökad användning av överskottsvärme.

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Till Herman

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List of papers

This thesis is based on the work presented in the following papers, referred to in the thesis by Roman numerals. The papers are not listed in chronological order by publication date, but rather in the order that makes it easier for readers to follow the structure of this thesis. The papers are appended at the end of the thesis.

I. Broberg Viklund, S., Johansson, M.T. Technologies for utilization of industrial excess heat: Potentials for energy recovery and CO₂emission reduction. Energy Conversion and Management 2014;77:369–379.

II. Broberg, S., Backlund, S., Karlsson, M., Thollander, P. Industrial excess heat deliveries to Swedish district heating networks: Drop it like it’s hot. Energy Policy 2012;51:332–339.

III. Broberg Viklund, S., Lindkvist, E. Biogas production supported by excess heat – A systems analysis within the food industry. Energy Conversion and Management 2015;91:249–258.

IV. Andersson, V., Broberg Viklund, S., Hackl, R., Karlsson, M., Berntsson, T.

Algae-based biofuel production as part of an industrial cluster. Biomass and Bioenergy 2014;71:113–124.

V. Broberg Viklund, S., Karlsson, M. Industrial excess heat use: Systems analysis and CO₂ emissions reduction. Applied Energy 2015;152:189–197.

VI. Ivner, J., Broberg Viklund, S. Effect of the use of industrial excess heat in district heating on greenhouse gas emissions: A systems perspective. Resources, Conservation and Recycling 2015;100:81–87.

VII. Broberg Viklund, S. Energy efficiency through industrial excess heat recovery – Policy impacts. Energy Efficiency 2015;8(1):19–35.

The co-author statement is presented in Section 1.3.

Other publications by the author not included in the thesis are the following:

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 Andersson, V., Broberg, S., Hackl, R., 2011. Integrated algae cultivation for biofuels production in industrial clusters. Working paper no. 47. Energy Systems Programme, Linköping University, Linköping, Sweden. (Prestudy for Paper IV)

 Andersson, V., Broberg, S., Hackl, R., 2012. Integrated algae cultivation for municipal wastewater treatment and biofuels production in industrial clusters.

Proceedings of WREF 2012, World Renewable Energy Forum 2012, Denver, CO, USA, 13–17 May 2012. (Early version of Paper IV)

 Andersson, V., Broberg, S., Hackl, R., 2013. Dubbel energivinst med alger som biobränsle [Double energy gain with algae as biofuels]. Energimagasinet no. 1.

(Popular science version of Paper IV)

 Backlund, S., Broberg, S., Ottosson, M., Thollander, P., 2012. Energy efficiency potentials and energy management practices in Swedish firms. Proceedings of ECEEE Industrial Summer Study on Energy Efficiency 2012, Arnhem, Netherlands, 11–14 September 2012.

 Broberg, S., Karlsson, M., 2013. Systems analysis and CO₂ reductions using industrial excess heat. Proceedings of ICAE2013, the 5^th International Conference on Applied Energy, Pretoria, South Africa, 1–4 July 2013. (Early version of Paper V)

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Acknowledgements

This work was carried out under the auspices of the Energy Systems Programme, which is financed by the Swedish Energy Agency. I gratefully acknowledge them for the financial support.

Although my name stands alone as the author of this dissertation, a long list of people contributed to my work as they all made this journey possible. Whether you made small or large contributions, or were just there for me, I am grateful to all of you. Thanks to..

… my supervisor Associate Professor Magnus Karlsson for your guidance and support and for your pep-talk when I felt that the hill in front of me was enormous.

… my co-supervisors Associate Professor Mats Söderström, Professor Jenny Palm, and Associate Professor Helen Peterson for all your encouraging words, valuable input to the work, and guidance through the academic world and its various methods.

… Per-Åke Franck, who commented on the draft of my thesis at my final seminar, for valuable comments and input that helped me improve this thesis and made me feel more prepared for my thesis defence.

… the participants in the industry seminar group and the division seminar group for commenting on my work throughout my years as a PhD student. Tanks for all your feedback!

… Sandra Backlund, Maria Johansson, Emma Lindkvist, and Jenny Ivner at the Division of Energy Systems for good cooperation and interesting and useful discussions when planning, preparing, and writing our papers. And, a big thanks to Jakob Rosenqvist for spending all those hours on the Gotland ferry helping us sort out the many terms and components.

… all my colleagues at the Division of Energy Systems for the good cooperation, enjoyable coffee-break discussions, wonderful homemade pastries, and a large share of bakery baked vetekransar. A special thanks to Sandra Backlund and Linda Olsson, for being my best PES friends throughout the years as a PhD student, to Klas Ekelöw for all those lunchpromenader where you share your knowledge of everything and nothing and for helping me solve all those little computer problems, to Elisabeth Wetterlund for introducing me to the life of the department and, as my first office neighbour, for letting me enjoy your of the day favourite song over and over again. And finally to Elisabeth Larsson for all your help with everything between heaven and earth and for answering my everyday questions.

… all the people in the Energy Systems Programme. A special thanks to Viktor Andersson and Roman Hackl for the good cooperation on the never-ending algae project,

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… all the energy managers who completed my questionnaires and answered my interview questions, and the energy manager at the studied food company for responding to our questions and endless e-mails, letting us visit, sharing valuable data with us, and for being our private taxi driver when visiting and sharing all interesting facts and must-sees in the neighborhood.

… to my old Tomelilla friends Josefine, Martina, and Sofie for making me what I am today and for still being such a big part of my life and, of course, for never letting me forget how to speak real Skånska – I said I would move back one day and now was the time!

… to all my (not so anymore) “new” Linköping friends, with special thanks to Elin, you were one reason why I even moved back for this PhD. I will never forget our breakfasts in Baljan, the everyday Extra horoscopes, our shoe-shopping days, our cocktail evenings on my balcony or in your pink-walled kitchen, “lagen om alltings jävlighet”, our hangover days eating chili cheese at Burger King, our girl-talk on the “never-ending subject” and the “secret list” one of those talks at campus resulted in, and of course “det är du värd”, because you always are!

… my family, mamma Ingrid and pappa Arne for helping me set my mind on things other than work and for believing in me even though I do not think you have ever really understood what it is that I have been doing for the past five years. Thanks also to my sister Linda for helping me keep my mind off energy systems and for bringing those wonderful children, Nora (theneverendingtalkinggirljustashermother) and Albert, into my life. Without you all I would not be the person I am today and come this far. And of course, thanks also to my “new family”, the Viklund family for bringing a lot of joy into my life and for making it possible to add this nice name to this book.

… finally, my husband Herman, for believing in me and supporting me through all the everyday challenges. You may not always believe it but I do love “your perfect imperfections” and I know that you love mine. You are the light of my life, your smile makes me melt, you make me never want to go to sleep and, if I do, to go up early so that I do not miss a single minute with you. Herman, I love you to the stars and back.

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Thesis outline

This thesis gives an introduction to, and a summary of the seven appended papers. The papers are appended at the end of the thesis. The structure of the thesis is as follows.

Chapter 1 introduces the thesis and its research area, and then presents the aim and research questions in focus, gives an overview of the appended papers, a co-author statement, and an overview of the research journey.

Chapter 2 briefly introduces industrial energy use and energy efficiency in industry, but focuses on the concept of industrial excess heat.

Chapter 3 presents an overview of European directives and energy policy instruments related to industrial excess heat.

Chapter 4 gives a brief introduction to the theoretical background of this thesis, i.e., systems analysis and various approaches to assessing greenhouse gas emissions from the use of electricity and biomass.

Chapter 5 describes the systems studied in this thesis.

Chapter 6 presents the methodologies used in this thesis and how they have been applied.

Chapter 7 summarizes selected results from the appended papers. The results are presented in relation to the research questions.

Chapter 8 presents a discussion of the studies performed and the conclusions of the thesis.

Chapter 9 presents an overview of areas of interest for future research.

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Abbreviations

CCP coal condensing power CHP combined heat and power COP coefficient of performance

CP current policy

DC district cooling DH district heating

EED Energy Efficiency Directive EMS energy market scenario

ENPAC energy price and carbon balance scenarios

EU European Union

EU ETS the EU emission trading scheme

FT Fischer-Tropsch

GHG greenhouse gas

HOB heat-only boiler

IEA International Energy Agency IO investment opportunity IS industrial symbiosis

Klimp Climate Investment Programme LCA life cycle assessment

LIP Local Investment Programme

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NPV net present value ORC organic Rankine cycle PCM phase-change material

PFE the Programme for Improving Energy Efficiency in Energy Intensive Industries

TPA third-party access

TPV Thermophotovoltaic

WW Wastewater

WWT wastewater treatment WWTP wastewater treatment plant

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1 Introduction

This chapter begins with a brief introduction to the thesis, followed by a presentation of the aim of the thesis and a description of the research questions posed. Next, the scope of the thesis and its delimitations are described. The chapter ends with a co-author statement and a description of the research journey.

During the part of the research process when energy managers at Swedish companies were being interviewed, I repeatedly heard statements such as “even if they (i.e., the district heating companies) get the heat for free, they do not want it” and “it does not matter what price we offer”, referring to that their heat was still not attractive to district heating (DH) companies. The “heat” referred to was industrial excess heat, a heat resource generated, for example, as a by-product of industrial production. But, what are the opportunities for using industrial excess heat?

Exchanges of by-products between companies have been discussed in previous research.

These studies sometimes demonstrate that exchanging, for example, energy, materials, and by-products through the integration of companies has positive effects in the form of, for example, improved resource efficiency, environmental benefits, and economic gains (Chertow, 2000; Martin and Eklund, 2011; Ellersdorfer and Weiss, 2014). The idea is that what is considered waste by one company may be valuable to another, and that these exchanges will result in competitive advantages. Throughout the present research, different approaches have been used to describe this situation, where a broader system boundary were used to emphasize the opportunities and benefits coming from collaboration (Chertow, 2000; Porter, 1998).

Benefits from the use of industrial excess heat, more specifically, have been highlighted. For example, through collaboration between actors, hot water streams that cannot be used in the company that produced them can beneficially be used somewhere else. The literature states that the use of industrial excess heat may provide both economic and environmental

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Climate change and its associated risks are well known today, and national and international policy measures are being taken to stop this negative trend. In “Europe 2020: A European strategy for smart, sustainable and inclusive growth”, the European Union (EU) presents strategic objectives for 2020. Seven focus areas were established and, under the heading of

“Resource-efficient Europe”, the EU set the “20-20-20” climate targets. These targets¹ call for a 20% reduction in GHG emissions (compared with 1990 levels), a 20% share of final energy use from renewable resources, and a 20% increase in energy efficiency (EEA, 2014;

European Commission, 2010). The targets were updated at the end of 2014 with new targets of 40%, 27%, and 27% for these three areas, respectively, by 2030 (European Commission, 2014a). Since the targets are partly interconnected, improved energy efficiency, for example through the use of excess heat, may reduce not only primary energy use but also GHG emissions.

Despite the targets and increased attention to energy efficiency, forecasts indicate that the EU’s energy-efficiency target might not be met (EEA, 2014; European Commission, 2011).

These forecasts indicate the importance of further energy-efficiency efforts. The potential benefits related to the use of excess heat make this resource valuable in efforts to achieve the EU energy and climate targets, and have in recent years been highlighted in EU policy (European Commission, 2012). Also, increasing globalization is putting pressure on industries as they are now facing greater competition from around the world, and energy- efficiency measures are claimed to be a way to handle this competition (Thollander et al., 2010). However, as the various parts of the energy system are entangled, introducing excess heat in an energy system will influence other parts of the system. This means that the consequences of using excess heat may be complex to assess. Given this complexity, a systems approach could be useful when studying the effects of excess heat use. Although it is a promising resource, industrial excess heat has been paid little attention in the scientific literature.

1.1 Aim and research questions

The aim of this thesis is to identify manufacturing industries’ opportunities to use industrial excess heat and thereby make positive contributions to industry, society, and the climate. The aim is set to understand how this resource could be used to improve energy efficiency and reduce industry’s climate impact.

This thesis addresses the following four research questions:

1. What is the current untapped potential for industrial excess heat in terms of quantity, quality, and carrier medium?

1 Based on each member state’s potential, national targets have been set. The Swedish “20-20-20”

targets entail a 40% reduction in GHG emissions, a 49% share of final energy use from renewable resources, and a 20% increase in energy efficiency.

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Chapter 1. Introduction

2. What are the implications of using different technologies and systems solutions based on the use of industrial excess heat?

3. How do different excess heat use options and energy market conditions influence global CO₂ emissions?

4. How does policy influence industrial excess heat use?

To achieve the aim of this thesis and handle its inherent complexity, as previously mentioned, the research questions were addressed by analysing a broad range of aspects, such as technical possibilities as well as climate, policy, economic, and resource aspects, which all affect the benefits of using excess heat. These factors are elucidated using a range of methods, both quantitative and qualitative, which enables the topic to be studied from various perspectives. Table 1 presents an overview of the research questions considered in each of the appended papers.

Table 1. The appended papers in which each research question is addressed.

Research question

Paper

I II III IV V VI VII

1 • • •

2 • • • •

3 • • • •

4 • •

This thesis provides information on industrial excess heat use for the industrial sector, researchers, and authorities. The intention is that this thesis can provide useful information for stakeholders, so they can make better-informed decisions regarding the use of industrial excess heat, and for policy makers when introducing new instruments that may influence industrial excess heat use. This is done to facilitate decisions related to industrial excess heat so that this industrial by-product can be used more efficiently, resulting in reduced GHG emissions. In addition, the ambition is that these results will provide the research community with insights into the opportunities, benefits, drawbacks, and preconditions associated with industrial excess heat use by illustrating how industrial excess heat integrate with various technologies, the energy market, and policy instruments.

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1.2 Scope and delimitations

This thesis applies a systems perspective to the use of industrial excess heat. In this thesis, excess heat refers to industrial excess heat unless otherwise specified. The focus is on manufacturing industries in Sweden, although other businesses have been considered as possible heat sinks in the appended studies of heat cooperation. Though excess heat can possess various characteristics, the focus here is on the heat’s quantity (i.e., amount of energy), temperature (i.e., quality), and in which carrier medium the heat can be found. The thesis does not evaluate whether or not the identified excess heat arose from a thermodynamically optimized process. Excess heat potential refers to the theoretical potential of untapped excess heat.

There are several excess heat-recovery options, both technologies and systems solutions, a number of which are examined here. The focus will be on excess heat used externally or for electricity production and the studied measures will be specified in connection with the results presented in the appended studies. Although the systems studied here are Swedish, the analysis applies a European energy systems perspective. Since unused excess heat may be regarded as “wasted”, this thesis assumes that using excess heat is something good. This assumption will be challenged, however, when studying the robustness of such use related to climate aspects. In this thesis, climate aspects are limited to the emission consequences of excess heat use, meaning the impact on the amount of GHG emissions. GHG is taken to include emissions of CO₂ (carbon dioxide), CH₄ (methane), and N₂O (nitrous oxide).

1.3 Paper overview and co-author statement

This thesis is based on the following seven papers. The following describes the appended papers as well as the authors’ contributions to each paper.

Paper I

Broberg Viklund, S., Johansson, M.T. Technologies for utilization of industrial excess heat:

Potentials for energy recovery and CO₂ emission reduction. Energy Conversion and Management 2014;77:369–379.

This paper presents the range of technologies for recovery and use of excess heat. The technologies are classified and presented in four categories: heat-harvesting technologies, heat-storage technologies, heat-utilization technologies, and heat-conversion technologies.

The paper also investigates, through a questionnaire, the amount of untapped excess heat in Gävleborg County and applies some of the studied measures to this untapped excess heat.

The energy use potential of these measures is presented and discussed together with the effect on the amount of global CO₂ emissions under different energy market conditions as of 2030.

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The paper was planned and written in collaboration with Dr. Maria Johansson, a postdoctoral fellow at Linköping University. Data on available excess heat in Gävleborg County were obtained from a questionnaire formulated and compiled by the author in collaboration with Dr. Sandra Backlund, formerly of Linköping University. Calculations of electricity generation from excess heat were performed by Maria Johansson. All other parts of the paper were calculated, analyzed and written jointly with Maria Johansson. The work was supervised by Associate Professors Magnus Karlsson and Mats Söderström.

Paper II

Broberg, S., Backlund, S., Karlsson, M., Thollander, P. Industrial excess heat deliveries to Swedish district heating networks: Drop it like it’s hot. Energy Policy 2012;51:332–339.

The paper estimates, through a questionnaire, the untapped excess heat in Östergötland and Örebro counties. Based on this unused heat resource, the paper discusses whether using this heat in DH would be influenced by altered DH market conditions, such as the introduction of a third-party access (TPA) to the DH network. The discussion is based on calculations of estimated investment costs and revenues, which give an indication of whether the realization of a TPA could enable profitable excess heat investments.

The paper was planned and written jointly with Dr. Sandra Backlund, formerly of Linköping University. Data on available excess heat in Östergötland and Örebro counties were obtained from a questionnaire originally formulated by Associate Professor Patrik Thollander, Linköping University and sent out by the Östergötland and Örebro county administrative boards. The data on excess heat were then compiled and calculations performed by the author of this thesis, while the economic calculations were performed by Sandra Backlund;

the analysis was carried out jointly. Associate Professors Magnus Karlsson and Patrik Thollander, Linköping University, supervised and commented on the work.

Paper III

Broberg Viklund, S., Lindkvist, E. Biogas production supported with excess heat – A systems analysis within the food industry. Energy Conversion and Management 2015;91:249–258.

Paper III examines a synergetic use of excess heat. The main aim was to study a change in

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The original idea for the paper came from the author of this thesis. The paper was then planned and written together with PhD student Emma Lindkvist, Linköping University. The necessary data were collected together with Emma Lindkvist with some help from technician Jakob Rosenqvist, Linköping University. Calculations of excess heat use were performed mainly by the author of this thesis, while calculations of biogas production were performed mainly by Emma Lindkvist; other calculations were performed jointly. Associate Professors Magnus Karlsson and Mats Söderström supervised and commented on the work.

Paper IV

Andersson, V., Broberg Viklund, S., Hackl, R., Karlsson, M., Berntsson, T. Algae-based biofuel production as part of an industrial cluster. Biomass and Bioenergy 2014;71:113–124.

Paper IV presents the outcomes of introducing a biorefinery concept in an industrial cluster.

The study investigated the replacement of a current wastewater treatment plant (WWTP) with a biorefinery that consists of combined algae cultivation and wastewater treatment (WWT) and the production of algae-based biofuels (i.e., biodiesel and biogas). The concept enables for the use of excess heat to provide an appropriate algae growth environment and flue gases as an algae nutrient source. This paper describes a possible use of excess heat in a synergistic setup. The heating requirements for the cultivation pond are also studied.

The original report (Andersson et al., 2011) on which this paper is based was planned and written together with Dr. Roman Hackl, formerly of Chalmers University of Technology, and Viktor Andersson, PhD student at Chalmers University of Technology. Calculations of WWT and algae growth were performed by Roman Hackl, calculations of biodiesel production by Viktor Andersson, and calculations of biogas production by the author of this thesis; the analysis was carried out jointly. This published article version of the work was written jointly with Viktor Andersson, who also performed the heat requirement calculations.

Roman Hackl commented on the manuscript throughout its preparation. Associate Professor Magnus Karlsson, Linköping University, and Professors Simon Harvey and Thore Berntsson, Chalmers University of Technology, commented on and supervised the work.

Paper V

Broberg Viklund, S., Karlsson, M. Industrial excess heat use: Systems analysis and CO₂ emissions reduction. Applied Energy 2015;152:189–197.

Paper V uses a combination of modelling and future energy market scenarios for 2030 to investigate the trade-offs between excess heat use for heating and cooling applications and heat-driven electricity production. The paper studies how excess heat can be used under different energy market conditions to minimize the system cost. Moreover, the paper examines the global CO₂ emission consequences of the optimal system solutions under the different energy market conditions.

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The idea for the paper came from the author of this thesis. The paper was planned together with Associate Professor Magnus Karlsson. The chosen model was constructed and run and the paper was written by the author of this thesis. Magnus Karlsson served as a sounding board for ideas and discussions during the work, as well as providing methodological support during the construction of the model. Building the model required data on available excess heat; these data were obtained from a questionnaire formulated and compiled by the author in collaboration with Dr. Sandra Backlund, formerly of Linköping University.

Paper VI

Ivner, J., Broberg Viklund, S. Effect of the use of industrial excess heat in district heating on greenhouse gas emissions: A systems perspective. Resources, Conservation and Recycling 2015;100:81–87.

This paper analyses and discusses system aspects of the use of industrial excess heat in DH.

The analysis is based on GHG emission calculations and the analysis is conducted in two steps: 1) the introduction of excess heat in a contemporary DH system using life cycle assessment (LCA) calculations and 2) calculations based on future energy market scenarios for 2020 and 2030 to further explore system aspects.

This paper was planned and written together with Associate Professor Jenny Ivner, formerly of Linköping University. Calculations based on future energy market scenarios were performed by the author of this thesis, while the LCA was performed by Jenny Ivner; the analysis was carried out jointly. Associate Professor Magnus Karlsson supervised and commented on the work.

Paper VII

Broberg Viklund, S. Energy efficiency through industrial excess heat recovery - Policy impacts. Energy Efficiency 2015;8(1):19–35.

In this study, eight interviews were conducted with energy managers at Swedish manufacturing companies. Excess heat is a resource that may be used to increase energy efficiency; accordingly, interviews were performed to reduce the knowledge gap regarding factors that influence excess heat use, to improve our understanding of why excess heat use

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Helen Peterson, a former research assistant at Linköping University now employed as Associate Professor at University of Gothenburg.

1.4 Research journey

When I started my PhD, my research was to be oriented towards industrial clusters, particularly addressing how industries are integrated within a cluster and the cluster’s connection with the surrounding society. In the interdisciplinary post-graduate school, the Energy Systems Programme, the first year as a PhD student mainly entailed participating in various courses within the programme’s course package. The last course that year was an interdisciplinary project conducted in collaboration with Viktor Andersson and Roman Hackl, two PhD students from Chalmers University of Technology whose research concerned a related topic. Based on our different research topics, a project was formulated the aim of which was to study the integration of an algae-based biorefinery in an industrial cluster. From the work on this project, Paper IV was born.

In parallel, I got involved in a project studying the untapped industrial excess heat in Östergötland and Örebro counties in Sweden, which resulted in Paper II. Paper II also touched on the interaction of energy policies and excess heat use. In combination with the work on the algae project, which examined a possible use of excess heat, this project was the starting point of my research into excess heat use.

After my first year, I started to look more into available excess heat in Swedish industry and into various ways of using this heat resource. This work resulted in papers I and V. Paper I further studied untapped excess heat in Sweden but also considered several technologies for using that heat. Paper V is partly based on Paper I but uses optimization to examine excess heat use under different energy market conditions. These two papers also consider the climate aspects of using excess heat, in terms of effects on CO₂ emissions.

As a PhD student in the Energy Systems Programme, I was encouraged to engage in interdisciplinary research. This led to the next part of my research journey, in which I saw new opportunities to highlight and analyse the use of excess heat from new points of view.

Paper VII accordingly uses interviews to study how Swedish industries reason about the relationship between excess heat use and policy instruments. One interview was with a Swedish food company’s energy manager, who mentioned that the company had just started to look into internal biogas production at the industrial site. This interview marked the beginning of the study that resulted in Paper III, which examined excess heat-supported biogas production at an industrial company, focusing on aspects such as climate impact and economics.

During the project on excess heat in Östergötland and Örebro counties, I got in touch with Associate Professor Jenny Ivner, working in the same project but at another division at Linköping University. A few years later, Jenny Ivner started working at my division, and

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again we started to discuss excess heat in DH. This discussion resulted in Paper VI, whose approach combines various research methods and time-frames to create an overview of the climate impact of the use of excess heat in DH. One of the methods, energy market scenarios, is used in several of the appended papers, whereas the other method, LCA, was added to gain a more reliable understanding of the prerequisites for and climate impact of the use of excess heat.

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2

2 Energy efficiency and excess heat

This chapter describes the context in which the constituent papers of this thesis were written. Industrial energy use, energy efficiency, and excess heat issues are presented.

2.1 Industrial energy use

The industry sector accounts for a large share of the final energy use in Europe (EU-28) as well as in Sweden. Approximately one-fourth of European (Eurostat, 2014) and two-fifths of Swedish (SEA, 2014b) energy end-use originates from industrial activities (see Figure 1 and Figure 2). A few sectors dominate the Swedish industrial sector in terms of energy use. This can be seen in Figure 2, which shows that the pulp and paper, iron and steel, and chemical industries accounted for almost 75% of the industrial energy use of approximately 146 TWh in 2012.

The Swedish industrial energy use constituted of the following energy carriers in 2012:

electricity (36%), DH (3%), biofuels and peat (40%), coal and coke (10%), oil products (8%), and natural gas (NG) and town gas (3%) (SEA, 2014b). The use of these fuels is associated with emissions of GHG. The industrial sector accounts for approximately one-fourth of the CO₂ emissions in Europe (EU-28) and in Sweden, corresponding to approximately 1000 and 11 million tonnes of CO₂ emissions, respectively, in 2012 (IEA, 2014). The industrial sector clearly contributes significantly to European and Swedish energy use, and consequently to the use of primary energy resources and GHG emissions. To prevent a global temperature increase of more than 2ºC, global GHG emissions have to be reduced significantly, i.e., more than 40% by 2050 (IPCC, 2014). In view of the above-noted industrial energy use, together with its GHG emissions, and increasing global industrial competition, efficient use of energy resources in this sector is necessary.

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Figure 1. Final energy use by sector in Europe (EU-28) in 2012. Data on energy use taken from Eurostat (2014). Eurostat (2014) specifies data for the “service” (13%) and “agriculture/forestry”

(2%) sectors, but in this graph the energy used in these sectors is included in the “residential and service” category to adapt the presentation to the Swedish energy use data illustrated in Figure 2.

Figure 2. Final energy use in Sweden in 2012 by sector. The bar to the right specifies the industrial energy use by industry. Data on energy use taken from SEA (2014b).

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Chapter 2. Energy efficiency and excess heat

2.2 Energy efficiency

Improving energy efficiency is said to be key to reducing climate impact and increasing industrial sector competitiveness. Energy efficiency relates to the ratio between energy input (input resources) and the services provided (output) (Pérez-Lombard et al., 2013). Improved energy efficiency usually means using less energy while still providing the same service output; however, improved energy efficiency can also mean maintaining the amount of energy input while increasing the services provided (Ryan and Campbell, 2012). The benefits of improved energy efficiency are stressed in the literature. Ryan and Campbell (2012) present these benefits at four levels: international (e.g., reduced GHG emissions), national (e.g., increased energy security), sectoral (e.g., increased industrial competitiveness), and individual (e.g., increased disposable income).

Several opportunities exist to improve energy efficiency in the industrial sector. Worrell et al.

(2009) review the opportunities for improved energy efficiency in industry. Among the sector-wide measures identified are improved motor system efficiency and energy recovery in the form of heat, power, and fuel recovery. Energy-efficiency improvement through industrial collaboration by exchanges of by-product, exchanges of excess heat, and integrated energy systems constitute the inter-industry opportunities. In addition, process-specific and management measures are enumerated (Worrell et al., 2009). Although energy-efficiency technologies and measures are well known, cost-effective technologies are not always implemented. This is referred to as the energy-efficiency paradox. The energy-efficiency gap is the difference between the current or expected future energy use and the optimal current or future energy use (Jaffe and Stavins, 1994). The existence of this gap can be explained by barriers to energy efficiency, where an energy-efficiency barrier can be defined as a

“mechanism that inhibits a decision or behavior that appears to be both energy-efficient and economically efficient” and that “prevent investment in cost-effective energy efficient technologies” (Sorell et al., 2004). Examples of such barriers are: limited access to capital (i.e., opportunities may be overlooked due to lack of funds); imperfect information (i.e., opportunities may be overlooked because of insufficient information on energy- efficiency potentials and technologies); and bounded rationality (i.e., opportunities may be overlooked due to lack of time or rule-of-thumb decisions) (Sorell et al., 2004). Policies can be used to overcome these barriers and encourage energy-efficiency measures.

In Europe, energy efficiency has steadily improved compared with energy use projections since the 2020 targets were set. However, part of the reduction in energy use can be

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2.3 Excess heat

2.3.1 Excess heat: origin and definitions

The large energy use in the industrial sector, the need for improved energy efficiency and the opportunities associated with the use of waste products from industrial processes direct our attention towards industrial excess heat use and associated opportunities and benefits. This thesis accordingly focuses on this industrial heat resource.

Industrial excess heat is an industrial process by-product characterized by lower exergy than that of the original energy carrier used in the production process in which it arose. No process achieves 100% efficiency and not all the energy added to a system comes out as useful work; rather, part of this energy is always emitted as heat. Carnot efficiency is given by Eq. (1):

ƞ_Carnot = 1 – (T_c/T_h) Eq. (1)

where T_h [K] is the temperature of the heat source (i.e., the higher-temperature medium) and T_c[K] is the temperature of the heat sink (i.e., the lower-temperature medium, e.g., the environment). This gives the maximum theoretical efficiency of a heat engine operating between two temperatures. The larger the temperature difference between the high- temperature medium, T_h, and the low-temperature medium, T_c, the higher the efficiency.

However, practical restrictions, such as the temperature limits of various materials, limit the realizable efficiency. For example, if the construction of a coal power plant can withstand 380ºC (T_h) and the cooling water is at a temperature of 40ºC, this would give a maximum efficiency of 52%, so almost half of the input energy would be released as heat. In reality, the efficiency would be even lower than the Carnot efficiency due to inefficiencies such as friction in the system (Wolfson, 2011). This relationship is illustrated in the schematic picture in Figure 3.

Figure 3. Schematic picture of a heat engine operating between two temperatures.

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The following general definition of excess heat is used in this thesis: Industrial excess heat is heat (bound in liquids, gases, or hot materials) generated in an industrial process and currently not used internally in the processes. There is no generally accepted uniform definition of excess heat, and several terms and definitions have been proposed and used throughout the literature, some of which will be described² here. Waste heat, surplus heat, secondary heat, and excess heat are all terms used to describe the heat rejected from industrial processes. Grönkvist et al. (2008) discuss two ways of defining excess heat:

“Excess heat is heat that is left over after an industrial process has become (thermodynamically) optimized” and “Excess heat [is heat] that cannot be used directly in the industrial process”. Both definitions are problematic, as it may be a complex task to determine when a process has been optimized, while one interpretation of the second definition would include industrial production intended to produce excess heat for DH networks (Grönkvist et al., 2008). In a report included in the IEA Annex³ on industrial excess heat recovery, excess heat is defined as “the heat content of all streams (gas, water, air, etc.) which are discharged from an industrial process in a given moment”. However, in addition to this general definition they presents a number of subcategories defining different shares of excess heat, such as technically and economically usable excess heat as well as green excess heat originating from biomass (Berntsson and Åsblad, 2015). All three definitions presented here refer to heat generated at an industrial facility, while in other contexts other types of heat are included. For example, in the EED, the term “waste heat”

also comprises heat generated at electricity generation plants (European Commission, 2012), and sometimes energy gases generated as a by-product of industrial processes are included (Grönkvist et al., 2008). Compiling a uniform definition is clearly not easy.

As the first definition of excess heat implies that the processes considered should be thermodynamically optimized, what is or is not “true” excess heat can be questioned. The concept is sometimes used to refer to the share of excess heat that can be used externally, after the share that is technically or economically usable internally has been deducted (Berntsson and Åsblad, 2015). Bendig et al. (2013) distinguish between avoidable and unavoidable heat flows, where avoidable heat flows refer to excess heat from a process that is not optimized and unavoidable heat flows to excess heat from a process that is optimized.

By making this distinction, it is claimed that one can avoid making investments that ultimately overlook more energy-efficient measures. This phenomenon is found in e.g.

Klugman (2008) where a paper mill designed their processes for heat deliveries to a DH network, thereby increasing its internal energy use. Berntsson and Åsblad (2015) also discuss the concept of true excess heat and try to define a reasonable level of internal heat recovery

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(Berntsson and Åsblad, 2015). What is clear from these discussions is that what does or does not constitute true excess heat is not clear.

The allocation of CO₂ emissions to excess heat may affect whether or not the use of excess heat is encouraged. If the aim is to achieve efficient resource use and reduce primary energy use, then excess heat use is likely desirable. In line with the assumption of this thesis, CO₂ emissions are generally not allocated to excess heat as it is considered a by-product of industrial production (Grönkvist et al., 2008; Gode et al., 2010). This zero-emission allocation principle can however be questioned if the industrial energy use increases to enable excess heat deliveries or if the industrial process in which it arose is not optimized (Grönkvist et al., 2008; Grönkvist and Sandberg, 2006).

2.3.2 Excess heat use opportunities

Instead of being wasted, industrial excess heat can be used for a number of applications, thereby offering various benefits. The heat can either be recycled in the process in which it arose or recovered and used in another process, either in the industrial plant or in other external applications. Examples of excess heat use in the industrial plant are steam generation, water preheating, and premises heating (Thekdi and Belt, 2011). Thekdi and Belt (2011) look into various excess heat-recovery options and rank them in the order in which they should be considered for improving energy efficiency. The same general hierarchy is discussed in Bendig et al. (2013) and in Law et al. (2013) based on economic factors. The following order of recovery options should be considered (Thekdi and Belt, 2011):

1. Reduction – the amount of excess heat should be reduced through efficient use of heat within the process.

2. Recycle – reuse excess heat within the process in which it arose.

3. Recovery – use excess heat in other parts of the industrial plant or externally.

4. Recovery – use the heat for power conversion.

As described in Section 1.2, this thesis focuses on points three (partly) and four, use of excess heat within the process in which it arose or internally at the industrial plant is not considered.

Several alternatives for the recovery and use of excess heat for external applications exist (Ammar et al., 2012). Broadly speaking, excess heat can be used for heating, cooling, and electricity production applications. Several technologies and systems solutions exist for these alternatives. In addition to these applications, heat exchangers, heat pumps, and radiation collectors can be used to make excess heat accessible for use. Also, heat storage can be used to overcome obstacles associated with intermittent heat flows and distances between heat source and heat sink. This section should not be seen as a comprehensive review of excess heat-recovery solutions; rather, it is intended to visualize the broad variety of opportunities for reusing this thermal resource.

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Using excess heat as a thermal source in DH is a well-known concept. Sweden has well-developed DH systems available in approximately 270 of 290 Swedish municipalities, divided into more than 450 DH systems. The supply temperature in Sweden is approximately 70–120ºC, depending on, for example, the season and weather conditions, and the return temperature is approximately 30–60ºC. Collaborations on excess heat use between industries producing the heat and DH companies resulted in about 7% of the DH energy supply originating from industrial excess heat in 2013 (Swedish District Heating Association, 2014;

Arnell et al., 2013). The largest share of industrial excess heat deliveries comes from energy- intensive industries such as the pulp and paper, iron and steel, and chemical or refinery industries, which deliver heat to approximately 60 DH networks (Swedish District Heating Association, 2010; Arnell et al., 2013). If the excess heat temperature is too low for direct deliveries, heat pumps can be used to increase the temperature, a solution currently used in several Swedish DH networks (Arnell et al., 2013). To increase the use of excess heat, regional DH systems are also being considered. Connecting several DH systems may also offer advantages of scale, such as more cost-effective electricity and heat production (Sandvall et al., 2015). Sandvall et al. (2015) and Karlsson et al. (2009) studied the integration of several local DH systems and an industrial companies in Sweden and concluded that such setups may reduce both primary energy use and CO₂ emissions (Sandvall et al., 2015;

Karlsson et al., 2009). The delivery of excess heat to Swedish DH systems has been fairly constant in recent years: the trend only indicates a slight linear increase with actual deliveries of approximately 3500–4200 GWh per year, as illustrated in Figure 4 (Swedish District Heating Association, 2014).

Figure 4. Excess heat input in Swedish DH networks, 2004–2012 (Swedish District Heating Association, 2014).

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seen in Europe and throughout the world (Rydstrand et al., 2004). Different technologies exist for cooling production, absorption cooling offering an alternative to compression chilling, which is driven by electricity. Absorption cooling uses the energy in a heat source, such as excess heat, to run a refrigeration system, i.e., the heat source is used to evaporate the refrigerant, only a small amount of electricity being needed for pumping. Lithium bromide (LiBr) and water-based⁴ absorption coolers are commercially available today for large-scale applications. In Sweden a number of energy companies (e.g., in Linköping and Gothenburg) have invested in absorption cooling equipment and provide customers with cooling through DC systems. The temperature of the heat used in absorption cooling production is normally 80–120ºC (Rydstrand et al., 2004; Arnell et al., 2013). Coefficient of performance (COP) values for absorption chillers are reported to range from approximately 0.5 to 0.8 (Rydstrand et al., 2004; Srikhirin et al., 2001).

Heat recovery also offers possibilities for electricity generation from excess heat, some of which will be discussed in this section. Research and development in this area has resulted in several types of recovery systems for this purpose has been developed and is still evolving (Thekdi and Belt, 2011). These options include Rankine cycles (e.g., the organic Rankine cycle, ORC), thermophotovoltaic (TPV) systems, and phase-change material (PCM) systems.

As can be seen in the numbered list at the beginning of this section, Thekdi and Belt (2011) recommend heat recovery for power conversion as the last option due to low efficiency that may lead to poor profitability.

The Rankine cycle, ORC, and Kalina cycle are all power cycles based on the principle of heat energy being converted into mechanical energy used to produce electricity. An external heat source, such as excess heat, is used to evaporate the process working medium. The traditional steam Rankine cycle may have limited use in excess heat-recovery applications because suitable heat should be hotter than 240ºC (Law et al., 2013). The ORC and the Kalina cycle offer new possibilities because they use different working media with lower boiling points and thus can operate with lower excess heat temperatures. A range of organic working media is available for the ORC process, while the Kalina cycle uses a mixture of ammonia and water (Ammar et al., 2012). A number of ORC plants are running worldwide on different heat sources (U.S. Department of Energy, 2008), and in Sweden plants are running on excess heat in water from two pulp and paper companies (Holmgren and Sjödin, 2008; OES Opcon group, 2015). Another low-temperature power cycle is the PCM cycle. A heat source is used to heat a working medium consisting of a paraffin mixture. The mechanical energy arising from the volume expansion of this mixture when it changes from solid to liquid state, and back again through cooling by water, is used to produce electricity in a generator.

Unlike the Rankine cycles, which use heat to produce electricity through conversion to mechanical energy, new technologies are being developed in which electricity is generated directly from the heat; one such technology is TPV systems. In TPV systems, the radiation

4 The water serves as a cooling medium (refrigerant) and the LiBr as a working medium (absorber).

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from high-temperature heat sources (>1000ºC) is used to produce electricity. The heat source is used to heat the emitter, which consequently emits electromagnetic radiation that is converted into electricity in a PV cell. However, these technologies are mainly in the developmental stage (U.S. Department of Energy, 2008; Bauer et al., 2004). A more thorough description of the alternatives for excess heat use and their efficiencies is presented in Paper I.

In addition to the technological opportunities discussed above, excess heat can be used in industrial collaborations in which the heat is used in nearby industrial plants or businesses.

This possibility will be further discussed in Section 2.4.

2.3.3 Excess heat availability

Despite the above discussed opportunities for excess heat use and considering data on current heat use, studies indicate that this resource still remains largely unused. Cronholm et al. (2009) calculate the excess heat potential in Sweden based on the total amount of excess heat delivered to the DH system and the amount of energy used in various industry sectors.

Based on the assumption that each company in a sector has the same ability to deliver excess heat, the potential was calculated and finally partly adjusted based on known prerequisites.

The theoretical potential totals 6.2–7.9 TWh per year, of which approximately half is used today (Cronholm et al., 2009). Connolly et al. (2014) estimate the excess heat potential in EU27 countries and identify the quantities that could be delivered to DH networks. Their estimate, which is based on European emission data combined with assumed CO₂ emission factors and heat recovery efficiencies, totals 2710 PJ of industrial excess heat annually, which is thought to be more than enough to cover future DH demands (Connolly et al., 2014).

Persson and Werner (2012) estimate the heat-recovery potential in EU27 countries’ DH systems based on current reported excess heat in DH systems, the figures being adjusted according to Member State best practices. Their theoretical assessment identifies that 430 PJ⁵ of industrial excess heat could be used in DH systems if applying Member State best practices (Persson and Werner, 2012). Studies also indicate that only 3% of the available industrial excess heat is currently being used in DH (Euroheat & Power, 2013). Bendig et al.

(2013) discuss the division of excess heat potential into resource and reserve potentials, where “resource” refers to a theoretical excess heat potential and “reserve” to a lower potential taking technological and economic restrictions into account (Bendig et al., 2013).

These excess heat resources can differ in nature and be found in gases (e.g., flue gases, air, and steam), liquids (e.g., water), and solids (e.g., heat in materials) (Thekdi and Belt, 2011).

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temperature requirements for delivery directly to a DH network, while secondary heat is lower in temperature and therefore needs upgrading before being used as DH (Cronholm et al., 2009; Arnell et al., 2013).

Studies of excess heat potentials as described in this section are mainly top–down studies;

bottom–up studies in the field are scarce, for example, as noted in Bendig et al. (2013) and Persson et al. (2014). The untapped excess heat potentials considered in this thesis are based on site-specific data. In bottom–up studies based on site-specific data, data may be collected not only on the quantity of excess heat but also on other aspects such as temperature and carrier medium.

2.4 System studies of excess heat

By broadening the system boundary, industrial excess heat that would otherwise be wasted can find new uses. This section presents a brief overview of system studies of excess heat.

The complexity of trade-offs between internal and external uses of excess heat has been examined. Svensson et al. (2008) develop an approach for determining whether it is more economic to use excess heat internally for electricity generation or externally as DH. The approach also takes account of the CO₂ emissions associated with the different uses. The approach is based on modelling with an expanded system boundary, that is, both the company producing excess heat and the energy company are modelled within the same system boundary when exploring conditions for favourable cooperation (Svensson et al., 2008). This approach is applied by Jönsson et al. (2008) to examine excess heat cooperation between a kraft pulp mill and an energy company considering different future energy market conditions. The study demonstrates that the trade-offs between internal and external use depend on several factors: energy market prices, type of heat production, and DH demand.

Optimization results indicate that external use, i.e., excess heat delivered to DH, is profitable if the recipient heating systems have small heat loads.⁶ In addition, external use results in larger emission reductions than does internal use (Jönsson et al., 2008). Morandin et al.

(2014) also found that it could be profitable to deliver excess heat from a petrochemical cluster to a DH system, but their accounting of the CO₂ emission consequences of these heat deliveries provided no clear indication of reduced regional emissions.

A conflict between excess heat use in DH and combined heat and power (CHP)-based heat production has been discussed in the literature, commonly being explained by favourable economic conditions. This conflict assumes that introducing excess heat in DH will necessarily displace other types of heat production. Current energy policy however in many cases prioritizes bio-based electricity production (for a description of the electricity certificate

6 Three sizes of DH systems were studied, small, medium, and large. The small system heat demand was set to 117 GWh in the study.

System studies of the use of industrial excess heat